Amorphous magnetic alloy materials have been extensively studied for commercialization because of their excellent electromagnetic properties. Particularly, Co-Fe-Si-B type amorphous alloys of specific compositions can achieve very low magnetostriction, and are very much expected to find applications as materials for magnetic heads, magnetic sensors, etc. Attempts have been actively made to improve their electromagnetic properties such as magnetic permeability and magnetic flux density by adding various elements to the Co-Fe-Si-B type amorphous alloys. For example, Japanese Patent Application (OPI) No. 102541/81 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application".) discloses that Mn is added to the above type alloy so as to make its crystallization temperature above the Curie point, and the Mn-containing alloy is heat-treated above the Curie point in an attempt to improve its electromagnetic properties. This patent document states that it has previously been known to improve the electromagnetic properties of a conventional amorphous alloy by heat-treating it above the Curie point (usually 300.degree. to 400.degree. C.) and cooling the heat-treated product; but that a Co-Fe-Si-B type amorphous alloy crystallizes during heat-treatment because its Curie point is higher than its crystallization temperature. However, it is described that by adding a suitable amount (0.5 to 10 atomic%) of Mn to the alloy, the Curie point is made lower than the crystallization temperature, and consequently, this alloy can be heat-treated and thus improved in electromagnetic properties.
Japanese Patent Application (OPI) No. 79052/82 (corresponding to U.S. Pat. No. 4,527,614 and European Pat. No. 50,479) discloses high-quality Co-type fine amorphous metallic wires circular in cross section which have a very uniform shape with a circularity of at least 90% and a diameter variation of not more than 4%.
An amorphous metallic ribbon produced by the one roll method by the present inventors from a conventional Co-type amorphous metal, for example, an alloy having the composition of Co-Fe-Si-B-Mn described in the above-cited Japanese Patent Application (OPI) No. 102541/81 had low magnetostriction, high magnetic permeability, and high saturation magnetic flux density, but when a bias magnetic field was applied to it, its magnetic permeability decreased abruptly. Specifically, a Co-Fe-Si-B-Mn type amorphous metallic ribbon having a thickness of about from 5 to 100 microns (.mu.m) and a width of from 2 to 100 mm produced by jetting a molten alloy of the Co-Fe-Si-B-Mn type onto a rotating cooling roll made of a material having high thermal conductivity such as copper markedly decreases in magnetic permeability under the influence of a bias magnetic field.
Such ribbon which decreases in magnetic permeability in a bias magnetic field cannot be used in practical applications because when it is applied, for example, to a coordinates reading device, signals obtained become abruptly weak due to even a slight bias magnetic field, for example by the influence of the earth's magnetism owing to the differences in the directions of east, west, south, and north, or by the influence of a magnetized body near the measuring instrument.
The Co-type fine amorphous metallic wires described in Japanese Patent Application (OPI) No. 79052/82 have superior electromagnetic properties and corrosion resistance, but their magnetic permeability decreases under the influence of a bias magnetic field. Hence, they are not fully acceptable as a material for a coordinates reading device, for example.